1. Technical Field of the Invention
The present invention relates to a light source device using a light emitting device such as LED (Light Emitting Diode) or the like, an illumination device using the light source device, a liquid crystal device using the illumination device, and an electronic apparatus using the liquid crystal device.
2. Description of the Related Art
Recently, liquid crystal devices have widely been used for electronic apparatuses such as a computer and a cell phone. The liquid crystal device generally comprises a liquid crystal sandwiched between a pair of substrates each comprising an electrode so that the orientation of the liquid crystal is controlled by applying a voltage between both electrodes to modulate light transmitted through the liquid crystal, to display an image.
On the basis of the system for supplying light to the liquid crystal, various known liquid crystal devices are distinguished into a reflective liquid crystal device having a structure in which external light is reflected by a reflector plate provided on the outer surface or the inner surface of one of both substrates, a transmissive liquid crystal device having a structure in which light is supplied to the liquid crystal in a planar manner by using an illumination device provided outside one of the substrates, and a transflective liquid crystal device which functions as a reflective type when external light is incident, and functions as a transmissive type when external light is insufficient.
As the illumination device used for the transmissive liquid crystal device, the transflective liquid crystal device, and the like, a conventional known illumination device has a structure comprising a light source device which emits light, and a light guide which broadens the light exiting from the light source device in a planar manner and causes the light to exit. As the light source device, a conventional known device has a structure in which light from a light emitting device such as LED or the like is emitted to the outside through a lens, as disclosed in, for example, Japanese Unexamined Patent Application Publication No. 62-105486. According to this publication, it is known that an aspherical lens is used as the lens.
However, the aspherical lens used in the light source device disclosed in Japanese Unexamined Patent Application Publication No. 62-105486 is nondirectional, i.e., it has no directivity in condensation of the light emitted from the light emitting device. In other words, it has the property that light can be condensed in any directions all round.
Although the non-directivity for condensation of light is a preferable property according to circumstances, it is an undesirable property according to circumstances. For example, like in the case in which light is desired to be supplied as much as possible to the light guide used in a liquid crystal device, when light is desired to be condensed in the height direction of the light guide, but not condensed in the width direction perpendicular to the height direction, the light source device having no directivity for condensation of light is unsatisfactory for effectively utilizing light.
The present invention has been achieved in consideration of the above problem, and a first object of the present invention is to provide a light source device capable of efficiently applying light to an object according to the shape of the object to which light is supplied.
A second object of the present invention is to enable incidence of light with high efficiency to a light guide in an illumination device comprising the light guide.
A third object of the present invention is to enable a bright display easy to see without changing the light emitting ability, i.e., power consumption, of a light source in a liquid crystal device in which light is supplied to a liquid crystal panel to perform a display.
A fourth object of the present invention is to provide an electronic apparatus capable of performing a bright display easy to see with low power consumption.